The overall goal of this proposal is to develop a non-invasive method to detect the infiltration of cluster of differentiation (CD)8+ T-cells responsible for -cell destruction in pancreatic islets in Type 1 Diabetes (IDDM) by magnetic resonance (MR) imaging. In vivo imaging of immune cells infiltration in real time would have significant impact in managing clinical IDDM, pancreas and/or islet cell transplantation and the understanding of the pathogenesis of IDDM Unfortunately, such non-invasive techniques are currently not available. Based on our prior experience in cell labeling with crosslinked superparamagnetic monocrystalline iron oxide nanoparticles, we synthesized a novel MR imaging probe with high affinity ligands to T-cell autoantigenic markers that allowed for high-efficiency intracellular magnetic labeling of the cells with subsequent detection by MRI. This probe specifically binds to highly diabetogenic T-cell receptor (TCR) on CD8+ T-cells from non-obese diabetic (NOD) transgenic mice, but does not recognize CD8+ T-cells from healthy NOD mice. Furthermore, in our initial imaging experiments in vivo we were able to see gradual accumulation of labeled CD8+ T-cells in mouse pancreas after adoptive transfer. In the current proposal, we are going to conduct imaging experiments using this probe to answer highly relevant biological questions regarding the mechanisms that drive the recruitment, activation and differentiation of autoreactive CD8+ T-cells. Specifically, we propose to image in vivo tracking of CD8+ T-cell recruitment to the islets and -cell mass loss depending on the avidity of recruited killer cells. The proposed studies are a logical extension of the feasibility experiments, and if successful, a transition of this research would be tested in clinical trials.